Wet Processing Introduction

1. Textile Engineering

2. 2
Presented by:
Mazharul Islam.
B.Sc. in Textile Engineering.
Dept. of Wet Process Engineering (WPE).
PTEC _ Session 2015-16 (10th Batch).
Email: tex.mazharul@gmail.com

3. INTRODUCTION
Wet processing and its main Divisions:
The process by which the textile mtls are treated associated with water is
called wet processing.
There are mainly 3 divisions of wet processing-
a) Pretreatment (or preparation)
b) Coloration (dyeing or printing)
c) Finishing
i) Pretreatment: The process, which are done to make the textile mtl
suitable for dyeing & printing are called pre-treatment. To ensure that
the textile has the right physical and chemical properties to enable it to
be colored or finish. Such as desizing, scouring, bleaching etc.
Purpose:
• To remove added and natural impurities from textile material
• Removal impurities to the maximum extent possible with
minimum effect on fibrestrength.
• To impart desirable properties to textile material 3

4. ii) Dyeing & printing: The process by which the textile mtl are
coloured by different types of dye or pigments, related chemicals required
water is called dyeing. Other definition: Dyeing is a chemical process
which involves the migration of the dye from the dye solution to the
surface of the fibresin the fabric being coloured, the diffusion of the dye
through the fibresand the fixing of the dye by chemical bonding.
And Localized application of dyestuff or pigments on fabric according to
the predetermined design is called printing.
iii) Finishing: The process by which the textile mtls are made suitable
for marketing to satisfaction/attraction of buyer are called finishing i.e.
calendaring, Flame retardant finish leveling, anti-creasing, mercerizing,
packaging etc.
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5. Sewing / Stitching
↓
Shearing & Cropping
↓
Singeing
↓
Desizing
↓
Scouring
↓
Bleaching
↓
Mercerization
↓
Coloration
(Dyeing and Printing)
↓
Washing
↓
Finishing
↓
Folding & Packaging
↓
Delivery
SEQUENCES OF WET PROCESSING
Singeing
↓
Desizing
↓
Scouring
↓
Bleaching
↓
Mercerization
Typically a woven Cotton fabric
would be prepared by sequence
of process as shown In case of
knitting Sizing step is not
Involved so desizing is not
required, and mercerization is
done only for cotton.
Preparation/Pretreatment
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6. Definition of some important terms:
1) Greyfabric: It’s the fabric coming from the loom state, no
chemical processing is applied on it.
2) Grey Checking & GreyTesting: Here the fabric is checked
carefully that is there any deformities or not. Here the yarn
density, number of ends & number of picks per unit length,
yarn strength is also examined. Proper repairing of the fabric
is also done here.
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7. (3) Stitching: To increase the length of the fabric for
making suitable for processing is called stitching. It is done
by plain sewing m/c.
(4) Brushing: To remove the loose fibre & loose ends of
the warp & weft threads is known as brushing.
(5) Shearing / Cropping: The process by which the
attached ends of the warp & weft thread is removed by
cutting by the knives or blades is called shearing. Shearing
is done for cotton & cropping for jute.
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8. (6) Sinzing: The process by which the protruding/projecting
fibres are removed from the fabrics by burning or heat to
increase the smoothness of the fabric is called sinzing. This
process is mainly done by gas flame.
(7) Desizing: The process by which the sizing mtls (starch)
are removed from the fabric is known as desizing. The sizing
mtls was applied at the warp yarns of the fabric at the time
of weaving.
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9. 8) Scouring: The process by which the natural impurities (oil, wax,
fat etc.) & added/external/advantatious impurities (dirt, dust etc.)
are removed from the fabric is called scouring. It is done by
strong NaOH.
9) Souring: The process by which the alkali are removed from the
scoured fabric with dilute acid solution is known as souring.
10)Bleaching: The process by which the natural colours
(nitrogeneous substance) are removed from the fabric to make the
fabric pure & permanent white is known as bleaching. It is done
by bleaching agent.
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10. (11) Mercerizing: The process by which the cellulosic mtls /
substance are treated with highly conc. NaOH to impart some
properties such as strength, absorbency capacity, lusture is
known as mercerizing. It is optional. If the fabrics are 100%
export oriented then it is done by highly conc. NaOH (48-52°
Tw).
(12) Coloration: Coloration is the process of providing the
fabric with color.
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11. (13) Washing: Washing is done by firstly cold wash, then
hot wash (80°C) & finally normal wash.
(14) Finishing: Finishing is the process of providing the
properties that customer will value.
(15) Delivery: After packing the fabroc is delivered to
the respective buyer
(16) Heat setting: The process by which the width of
the fabrics are adjusted by heat is called heat setting.
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12. (17) After treatment: The process by which the loose dyes are
removed from the dyed fabrics to increase the lusture & fastness
property of the fabric is known as after treatment.
(18) Calendaring: It is done to remove the undesirable creese &
crinkle.
(19) Steaming / Curing: To fix up the dyestuff / pigment with
the fabric. Steaming is used for dyestuff & it is done in 100-105°C.
curing is used for pigments & it is done in 120-180°C.
(20) Stentering: It is done to increase/adjust the width of the
fabric.
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13. Pdf download link: Edu-Expert YouTube channel.
References:
1. Chemical Technology in the pretreatment Processes of Textiles (S.R.
KARMAKAR)
2. Textile Preparation & Dyeing (A.K. Roy Choudhury)
3. Chemistry & Technology of fabric preparation & finishing (C. Tomasino)
4. www.bdtextileinfo.blogspot.com
5. Wet Processing-I slide. (MD. MH Tomal, Lecturer, BUTex)
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14. Thank You !
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